1. Field of the Invention
The present invention relates to a focus detection apparatus having a function of automatically adjusting a focus, and a focus detection method.
2. Description of the Related Art
There has conventionally been known a focus detection unit of a so-called phase difference detection method as a focus detection unit of a camera discussed in Japanese Patent Application Laid-Open No. 9-054242. In this method, light fluxes from a subject, passing through different exit pupil areas of a photographing lens, are imaged on a pair of line sensors, and a displacement amount, between relative positions of a pair of subject images obtained through a photoelectric conversion of the subject images, is obtained. Then, a defocus amount of the subject is detected, and the photographing lens is driven based on the detected defocus amount, whereby a focus of the photographing lens can be adjusted.
Japanese Patent Application Laid-Open No. 9-054242 also discusses that, in order to obtain defocus amount at a plurality of range-finding points, a plurality of line sensors, each corresponding to each range-finding point, are provided in a focus detection sensor to perform a focus detection.
On the other hand, there has been known that, as a method for detecting defocus amount at other plurality of range-finding points, a pair of line sensors is divided into a plurality of areas, and a focus detection unit detects the defocus amount at each area. For example, in Japanese Patent Application Laid-Open No. 2006-220684, a line sensor is divided into plural areas, and the defocus amounts at the respective areas are detected. Japanese Patent Application Laid-Open No. 2006-220684 also discusses that line sensors are coupled to make one line sensor so as to increase a focus detection area, whereby a large defocus amount can be detected.
However, in the focus detection unit discussed in Japanese Patent Application Laid-Open No. 9-054242, the size of the focus detection sensor is limited, so that there is a limitation in the number of the range-finding points.
The focus detection unit discussed in Japanese Patent Application Laid-Open No. 2006-220684 needs a frame memory or a circuit configuration that can transfer an accumulation signal to each frame memory with non-destroyed manner, to detect the defocus amounts of the respective divided areas.